I've had a few powerlinks that were tight but they really do come apart.

I push the inner links together while wiggling the chain at that point, side to side. Keep an eye on the slot the powerlink pin heads travel through and you'll know when it can come apart or it will come apart at that point anyways.

Perhaps putting the drive train in small/small will take more of the rear derailleur tension off the chain as well.

Can someone point me to the old thread that shows how to do this? I'm having a very tough time removing my chain. Thanks in advance!

Sometimes it's easy and other times its hard. First thing to do is clean the link so that no gunk will prevent the pin from sliding to the bigger hole. Lazy me usually skips the cleaning part and use pliers, pressing from opposite corners of the link.

Press the plates together and push both pins inwards until it unlocks. Lube the link and clean it if possible. Crud will make it extremely difficult to remove. With enough use powerlinks can deform to the point it is no longer possible to seperate them and you'll just need to use a chaintool to break the chain.